Influence of Inner- and Outer-Sphere Electron Transfer Mechanisms during Electrocatalysis of Oxygen Reduction in Alkaline Media

2011 ◽  
Vol 115 (36) ◽  
pp. 18015-18026 ◽  
Author(s):  
Nagappan Ramaswamy ◽  
Sanjeev Mukerjee
Keyword(s):  
Electron Transfer ◽  
Oxygen Reduction ◽  
Outer Sphere ◽  
Alkaline Media ◽  
Outer Sphere Electron Transfer ◽  
Transfer Mechanisms

scholarly journals Fundamental Mechanistic Understanding of Electrocatalysis of Oxygen Reduction on Pt and Non-Pt Surfaces: Acid versus Alkaline Media

2012 ◽  
Vol 2012 ◽  
pp. 1-17 ◽  
Author(s):  
Nagappan Ramaswamy ◽  
Sanjeev Mukerjee
Keyword(s):  
Electron Transfer ◽  
Oxygen Reduction ◽  
Active Site ◽  
Electrode Materials ◽  
Strong Dependence ◽  
Outer Sphere ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Wide Range ◽  
Inner Sphere

Complex electrochemical reactions such as Oxygen Reduction Reaction (ORR) involving multi-electron transfer is an electrocatalytic inner-sphere electron transfer process that exhibit strong dependence on the nature of the electrode surface. This criterion (along with required stability in acidic electrolytes) has largely limited ORR catalysts to the platinum-based surfaces. New evidence in alkaline media, discussed here, throws light on the involvement of surface-independent outer-sphere electron transfer component in the overall electrocatalytic process. This surface non-specificity gives rise to the possibility of using a wide-range of non-noble metal surfaces as electrode materials for ORR in alkaline media. However, this outer-sphere process predominantly leads only to peroxide intermediate as the final product. The importance of promoting the electrocatalytic inner-sphere electron transfer by facilitation of direct adsorption of molecular oxygen on the active site is emphasized by using pyrolyzed metal porphyrins as electrocatalysts. A comparison of ORR reaction mechanisms between acidic and alkaline conditions is elucidated here. The primary advantage of performing ORR in alkaline media is found to be the enhanced activation of the peroxide intermediate on the active site that enables the complete four-electron transfer. ORR reaction schemes involving both outer- and inner-sphere electron transfer mechanisms are proposed.

Outer-sphere electron transfer between (cyclam)nickel(2+) and copper(III) imine-oxime complexes

1989 ◽  
Vol 28 (1) ◽  
pp. 157-160 ◽  
Author(s):  
Ashiq Hussein ◽  
Yousif Sulfab ◽  
Mohamed Nasreldin
Keyword(s):  
Electron Transfer ◽  
Outer Sphere ◽  
Outer Sphere Electron Transfer
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